Human carcinoma of the prostate will be transplanted into nude mice using new experimental approaches, to try to avoid previous failures. One innovation is the implantation into the testis made alymphatic by surgical division of lymphatic channels in the cord. This will have the advantages of a high androgen environment, combined with a naturally privileged site made even more privileged by the surgery. The second innovation is the co-implantation of radiated mouse tumor cells as a source of tumor angiogenesis factor to stimulate ingrowth of host vessels. The behavior of the prostate and testis as immunologically privileged sites will be studied by the implantation of antigens (SRBC wall, skin grafts) into their parenchyma. The effect of a privileged site on carcinogenesis will be determined by the rate of tumor development after carcinogen injection into the prostate and testis of normal vs. nude mice. Achieving routine growth may permit determination of hormonal dependence of individual prostate tumors, with clinical application.